This invention relates to a method and apparatus for composting waste and for compost resulting from such method and use of such apparatus.
It is currently known to dispose of animal bodies such as poultry by depositing these in an essentially open container and letting these decompose.
A number of problems exist with current composting practices a first of these being a problem of obnoxious smell, a second problem relates to biosecurity where infections resulting in pathogens, can be either released or cross infect other environs, and a further problem relates to disposal of material even when composted if it is not biologically safe.
I have discovered then that if the composting materials are held in a closed container and the air in the system only is recycled through the composting materials, then this provides significant benefits.
In other words by recirculating over a substantial time only the air and gaseous materials that already exist or are being formed within a closed circuit, then this has surprisingly beneficial results.
What has been discovered is that such a method can firstly result in reduced strength of obnoxious smell that has hitherto plagued disposal of animal bodies and it is not entirely clear as to why this happens.
Further, while it has been known that ammonia is a possible product of rotting protein materials it has been conventional for others to try to minimise this as it is considered to lead to a loss of nitrogen in eventual compost. In so far that any composting process uses replacement air even if some recirculation takes place then by maintaining recirculation only with the internal gases and no deliberately introduced outside air, the level of whatever is the gaseous discharge of the composting microflora will build up.
A further result of recirculation of only internal gaseous materials is that gases which may be warmed from the composting process will stay warm and will transfer that warmth through the mass of materials without outside refreshing air either generally or in parts cooling this.
Biological processes during composting are implicitly complex
What appears to happen is that ammonia as a gas builds up in concentration and rather than this being a disadvantage it has significant advantage in providing at the least assistance in sterilisation in respect of pathogens.
A significant advantage of ammonia build-up is that this material is effective in killing a broad spectrum of pathogens while not apparently inhibiting continued composting breakdown of the composting materials. Further, the microflora that is promoted seems to be such that odiferous output is relatively low.
Given that the composting materials also produce heat, there appears to be the additional benefit of both increased heat together with an ammonia buildup which provides for an effective better pathogen kill in relation to the composting materials.
In one form of this invention then, this can be said to reside in a method of treating materials to be composted which includes the steps of containing such materials within a closed container, pumping air into the container at one part of the contained body of material, and taking the air having passed through the material from the container so that it, and it only, will be substantially recirculated back to an introduction location of the material so that gaseous products of any decomposition of the materials will be kept within the container or its connected conduits.
In preference, there are means to effect a cyclic operation of such a pump so that it can be switched on and switched off over a decomposing period according to a pre-arranged program.
In preference, there is proposed a method of effecting composting of materials having a high protein content which includes the steps of containing such materials within a closed container, pumping air into the container at one part of the contained body of material, and taking the air having passed through the material from the container so that it will substantially recirculate back to an introduction location of the material only air and any gaseous compost product.
In preference, there is a biofilter in the pathway of such recirculating air.
In preference, such biofilter includes compost through which the air and gaseous product to be filtered is passed.
In preference, the inlet conduit into the container is arranged to introduce air to a top of the container so that the top of the container acts as a plenum with air at pressure then being pushed downward through a mass of material to be composted to collect apertures within a base of the conduit.
In preference, the base of the container includes a plurality of tubes having apertures therein which are laid to extend across a floor of the container and which are collectively connected to a conduit directed to an inlet of the pump.
In preference, the container includes an uppermost pivot supported lid.
In preference, the material to be composted comprises the bodies of dead poultry and the packing of the container includes a first covering of woodchips then successive layers of bodies of poultry, a layer of woodchips, a layer of poultry and so on.
Further, it has been discovered that if such recirculation occurs on a regular basis through a decomposing period which can be several weeks, nonetheless, such treatment is sufficient to maintain a dominance of aerobic bacteria with significant improved results.
By maintaining what is in effect a closed circuit arrangement, then any odours are substantially contained within the circulating equipment.
While various filters can be used to minimise the extent of odour that might be released when the doors are opened to either empty or reload the container, a filter material that has been found to be very useful has been compost which has been made more porous by having this distributed with pine chips.
In one form of the invention then it could be said to reside in a method of composting which includes the steps of placing the materials to be composted into a container, sealing the container and then blowing in a recycling manner substantially only the air and gases contained within the container through the composting materials for a period of time to collect and distribute ammonia sufficient to allow for a substantial buildup in concentration to a pathogen killing level of ammonia derived from the composting materials, and then maintaining such circulation for a sufficient period of time so as to effect a substantial pathogen kill in the composting material.
The method has the additional advantage that because the air and gases are simply recycled and are not bled out to atmosphere whether or not through a filter, means that there is no difficulty in having such a container in the vicinity of habitation.
It is well known that the putrid smell of rotting carcasses can be considered most offensive and is highly objectionable and will be objected to by many people.
A further advantage of the method described is that ammonia being recycled can of itself be separated and be used for other useful purposes such as conversion to fertilizer for instance by passing the nitrogen-rich gases through sulphuric acid to form ammonium sulphate as one example.
If the container is made of an uppermost lid that can be lifted to allow access into the body of the container, then the temporary opening of this lid and insertion of birds will not of itself substantially interfere with the process described.
The apparatus to perform the method includes a container, a lid that can assume two positions, one of which provides for an airtight seal with respect to the container, and means to effect to circulation of air where there is a manifold extending across a part of the container, which manifold is connected to air blowing means, and a further conduit from the airblowing means to effect direction of air to or from a further portion of the container which is opposite to that in which the manifold is located.
In preference, such an arrangement has the manifold extending across a bottom of the container, and air is introduced into a space at the top of the container between the lid and the composting materials, and there are means to effect a switching on and off of the air blower in accordance with a selected procedure.
Such a selected procedure may be to effect a blowing of the air and gases for a period of five minutes each hour or it may involve a longer period of blowing over different periods of time.
In preference, the composting materials are placed in layers with materials separating the respective layers which are porous.
In this way, air that is being pumped through the composting material, will as it passes successive layers redistribute in the porous intervening layer and pass through the next composting materials layer to the next more open or porous layer.
What we have now is that a container or bin of relatively substantial size such as a bin appropriate for transport on a truck without the need for excess width warnings, is placed at a convenient location for receiving composting materials such as dead poultry.
The poultry is placed in layers with intervening porous materials on to a lower manifold of pipes with a plurality of apertures throughout the length of the respective pipes to effect therefore a distributed passage of air and of course gathered gases.
Once loaded, the container has a lid that is openable from the top for loading of the chickens but thereafter closed in such a way as will provide an effective air seal.
From here, the program is set to circulate air on a regular basis but only on the basis that it is the air that is captured within the bin and any composting gases that are formed.
Because the material is in a closed container, and the air recirculating devices in preference are external but nonetheless sealed from allowing any additional outside air to be introduced.
By continuing this program for a period, the rotting carcasses will start to decompose and in an environment that is slowly changing from aerobic to anaerobic, it is found that there is a nitrogen buildup in the form of ammonia which is then transferred through all of the stored composting materials.
By recycling over a significant period of time without refreshing the air within the recycling path, results in a significant buildup of this alternate gas which has the significant beneficial advantage that this will then assist significantly in the pathogen kill off.
The invention then can also reside in the method of treatment of waste which includes the steps of placing the waste in a container, recirculating air through the waste held in the container so as to at least for a substantial period of time, recirculate only that air and any gaseous product of decomposition of the waste.
In preference, the container is such that it can be opened for introduction of and removal from waste from the container, and has a access lid which can close the container against any substantial air access outside of the container.
Preferably, the process described is continued until a substantial concentration of ammonia is built up within the circulating air whereby to effect a substantial kill off of any pathogens within the refuse.
In preference, the refuse includes materials having substantial protein content